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    /* 基础样式 */
    .book{
       margin:10px ;
       padding:15px;
       border:1px solid #ccc;
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    [data-category="科幻"]{
        background-color: #007bff;
        color:#fff;
    }
    [data-category="历史"]{
        background-color: #8b4513;
        color:#fffdd0;
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    [title^="入门"] h2::before{
        content:"🌟";
        margin-right:5px;
        font-size: 1.2em;
    }
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<body>
  <div class="book" data-category="科幻">
    <h2>三体</h2>
    <p>作者：刘慈欣</p>
  </div>
  <div class="book" data-category="历史">
    <h2>明朝那些事</h2>
    <p>作者：当年明月</p>
  </div>
  <div class="book" data-category="小说">
    <h2>活着</h2>
    <p>作者：余华</p>
  </div>
  <div class="book" data-type="语言学习" title="入门日语初级课程">
    <h2>日语初级课程</h2>
    <p>学习日常对话和基本语法</p>
  </div>
</body>
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